Production of alkylated aromatic hydrocarbons



April 8,- 1947.

BENEI'DICT Er AL 2,418,689

PRQDUCTION OF ALKYLATED AROMATIC HYDROCVARBONS Filed Nov. 10, 1943Patented Apr. 3, 19447 FFIC'E IPRDUCTION F ALKYLATED AROMATICHYDROCARBONS Wayne L. Benedict, Chicago, and William J. Mattox,Riverside, ill., assignors to Universal Oil Broducts Company, Chicago,Ill., a corporation of Delaware Application November 10, i943, SerialNo.509,680

(Cl. 26o-671) i1 claims; i

The invention relates particularly to the production of di-alkylaromatic hydrocarbons by a.

series of interdependent and cooperative steps in which a suitablealiphatic or naphthenic hydrocarbon containing at least 7 carbon atomsto the molecule is subjected to aromatization to produce mono-alkyl andtri-alkyl aromatic hydrocarbons, the mono-alkyl aromatic hydrocarbonbeing subjected to alkyl transfer reaction to produce the di-alkylaromatic hydrocarbon and benzene, and the benzene being reacted withsaid tri-alkyl aromatic hydrocarbon to produce additional quantities ofsaid di-alkyl aromatic hydrocarbon.

The charging stock tothe process comprises a paraiinic and/or olenichydrocarbon having at least 6 carbon atoms in a straight chain and/or analkyl cyclohexane having at least 7 lcarbon atoms to the molecule. Itmay suitably com- 'prisehydrocarbon fractions containing one or more ofthese aliphatic and/or naphthenic hydrocarbons having 7, 8 and/or 9carbon atoms per molecule, which fractions may or may not containaliphatic and/or naphthenic hydrocarbons having 6 carbon atoms to themolecule, such as normal and cyclohexane, and/or higher boilinghydrocarbons, such as those containing 10 or more carbon atoms permolecule. A particularly suitable charging stock may comprise selectedfractions of straight run gasoline containing hydrocarbons having 6 to 9carbon atoms per molecule.

In accordance with the present invention, the charging stock issubjected to aromatization under aromatizing conditions and in thepresence of suitable aromatization catalysts including, for example, theoxides of chromium, molybdenum, vanadium, etc., which preferably aredeposited on aluminum oxide or other appropriate supports.

alkyl aromatic hydrocarbon, is so treated in order to produce xylene andbenzene. 'The benzene is then reacted with the tri-alkyl aromatichydrocarbon in the presence of selectedtatalysts under selectedconditions of operation to produce additional yields of the di-alkylatedaromatic hydrocarbon. Thus, for example, trimethylbenzene is reactedwith the benzene to produce additional yields oi xylene.

Xylenes are at present in demand for various important uses. It hasrecently been shown that xylenes are particularly desirable 'forblending in gasoline and particularly *in aviation gasoline.Ortho-xylene is utilized as an intermediate in the preparation ofphthalicV acid or similar compounds.

`hydrocarbon which comprises subjecting hydro- In the aromatization stepof the process, thel aliphatic hydrocarbons are subjected to cycllzationand dehydrogenation, while the naphthenic hydrocarbons are subjected to'dehydrogenation, in order to produce the corresponding mono-alkylaromatic hydrocarbon.` However, tri-alkyl aromatic hydrocarbons are alsoproduced during the aromatization step of the process, and it is anobject of the present invention to convert s'aid mono-alkyl andtri-alkyl aromatic hydrocarbons into'substantial yields of di-alkylaromatic hydrocarbons. In accordance with the invention. the mono-alkyl`aromatic hydrocarbon is subjected to conversion in the presence ofselected catalysts under selected conditions of operation to produce a.di-alkyl aromatic hydrocarbon and benzene. For example, toluene, whichis a monocarbons containing at least 7 carbon atoms to the molecule toconversion under conditions to produce mono-alkyl and tri-alkyl aromatichydrocarbons, subjecting said mono-alkyl aromatic-hydrocarbon to alkyltransfer in the presence of an alkyl transfer catalyst under conditionsto produce said di-alkyl aromatic hydrocarbon and benzene, andsubjecting said benzene and tri-alkyl aromatic hydrocarbon to alkyltransfer in the presence of an alkyl transfer catalyst under conditionsto produce said di-alkyl aromatic hydrocarbon,

In one specific embodiment, the present invention relates to a processfor the production of xylene which comprises subjecting a hydrocarbonfraction containing straight chain paraiiinic hydrocarbons having from 6to 9 carbon atoms per molecule t'ol aromatization in the presence of analumina-chromia catalyst under aromatizing conditions to produce tolueneand trimethylbenzene, subjecting said toluene to contact with asilicaalumina catalyst at a temperature of from about 500 to about 700C. to produce xylene and benzene, subjecting said benzene to reactionwith said trimethylbenzene in the presence of a silicaalumina catalystat a tempertaure of from about 400 to about 700 C. to produce additionalquantities of xylene.

In another aspect the present invention relates to a process forproducing a di-alkyl aromatic hydrocarbon from a mono-alkyl aromatichydrocrbonby reacting the latter in the presence of an allwl transfercatalyst under conditions to produce the di-alkyl aromatichydrocarbonand benzene.

steps oi the present process may be the same or different and maycomprise composites of silica and one or more refractory oxides such asalumina, zirconia, thoria, magnesia, etc., which are referred to in thepresent specification and claims as silica-alumina catalysts. Inaddition the catalyst maybe further modified by .incorporating thereinother refractory oxides such as molybdena, vanadia, chromia, etc. Thecatalyst of the present invention is preferably synthetically'preparedand may be formed by the separate or simultaneous precipitation of thecomponents and preferably is followed by purification to substantiallyremove alkali and alkaline earth vmetal compounds.

Other suitable alkyl transfer catalysts may be employed such as a solidphosphoric acid catalyst which comprises a composite of phosphoric acidand kieselguhr or other suitable carrier. It is understood that thesevarious catalysts are not necessarily equivalent in their activity oreffec-I carbons being reacted therein but these conditions Will bewithin the range heretofore specified. For example, in the alkyltransfer reaction of the mono-alkyl aromatic hydrocarbon, it may bestated in general that as the alkyl side chain on the aromatichydrocarbon increases, the temper..

ature to be employed for its conversion decreases.

Thus, ethylbenzene may be satisfactorily converted at a lowertemperature than toluene: the former at a temperature of from about 200to about 600 C. and the latter at a temperature of from about 500 toabout '700 C. However, the temperaturaprssure and space velocity will becorrelated to produce the desired results.

As used herein,v the term "hourly weight space velocity" is intended tomean the Weight of oil per hour per weight of catalyst inthe reactionzone.

The invention will be further explained in describing the accompanyingdiagrammatic ow drawing which illustrates one specific embodiment of theinvention but not with the intention of unduly limiting the same.v

Referring to the drawing, a suitable charging stock as heretofore setforth is introduced to the process through line I and is directed intoarothe type now known in the art as flxed bed,

fluidized,` or slurry operation. Aromatization is usually effected at atemperature within the range of from about 450 to about 700 C., apressure of from substantially, atmospheric to 1000.

pounds or more per square inch, at a weight hourly space velocity offrom about 0.1 to 5 or more. These conditions are preferably correlatedin order to produce high yields of aromatic hydrocarbons per pass.

It is also within the scope of the invention to `effect thearomatization reaction during the reforming of gasoline boiling rangefractions such as straight run gasoline, which reforming may be effectedeither in the presence or absence of hydrogen. Likewise, it is Withinthe scope. of 'the invention that aromatization in zone 2 may beeffected in the absence of a catalyst, but it is preferred in thisembodiment of the invention that substantial yields of aromaticsare'produced per pass. f

The aromatization Aproducts are directed through line 3 into separationzone 4, which may comprise one or a plurality of suitable fractionating,absorbing and/or stripping zones, whereby the products introducedtheretormay be separated into the desired fractions. In-the casehere'illustrated,-light Ihydrocarbons boiling below benzene may bewithdrawn from the upper portion of zone 4y through line 5 and may beremoved from the process. A benzene-containing fraction is withdrawnfrom z'one- 4 through line 6 andmay be removed from the process, butpreferably at least a portion thereof is directedv through line 1 forfurther conversion within the process in the manner to -be hereinafterset forth. A toluene- I containing fraction is withdrawn through line 8and, whilea portion thereof may be removed from the process, at least aportion thereof is directed through line 9 for further conversion in themanner to be hereinafter set forth.

When desired, an ethylbenzene fraction may be separated in zone 4 andwithdrawn therefrom through line I0. A xylene-containing fraction iswithdrawn from zone 4 through line Il, While a curnene-containingfraction is removed fromzone 4 through line I2; A fraction containingtrimethylbenzene is withdrawn from zone 4 through line I3 and, while aportion thereof may be removed from the process, at least a portion beremoved from the process.

It is understood that the separation illustrated in the drawing isspecific to an operation in which the charging stock supplied toaromatization in zone 2 contains straight c-hain aliphatic hydrocarbonshaving 1, 8 and 9 carbon atoms to the molecule or to a charging stockcontaining alkyl cyclohexanes in which the alkyl groups comprise methyl,ethyl and isopropyl radicals .or to mixtures of these aliphatic andnaphthenic hydrocarbons. The charging stock may or may not containnormal hexane and/or cyclohexane.

In cases Where the charging stock'contains other hydrocarbon compounds,separation in zone 4 may be modified accordingly to separate theproducts as desired. It is also within the scope of the invention tosubject either the total products from zone 2 or any desired fractionthereof to solvent extraction or other treatment in order to separatethe aromatic hydrocarbons from unconverted` paraftlns and/or naphthenes.The unconverted paraiims and naphthenes may be recycled, by well known4means not illustrated, to the aromatization zone for further treatmenttherein, while4 the aromatic hydrocarbons may be recovered in part orsubjected to further treatment in accorda-nce with the presentinvention.

When the aromatic-containing fractions withdrawn from Vzone 4 forfurther treatment within the process contain substantial quantities ofoleiins, it may be desirable to subject these fractions, either togetheror separately, to .an olefin removal step prior to the alkyl transferreactions.'v

The presence of substantial quantities of olens as. for example, inexcess of to 20%. may reene'into xylene and benzenemay be effected inthe presencerof a silica-alumina catalyst -at a temperature of fromabout 500 to about 700 C., a pressure of from about atmospheric to about1000 pounds or more and preferably of from about 200 to about 500 poundsper square inch, witha weight hourly space velocity of from about 0.1 toabout 10. Zone i6 may be of either a fixed bed, iluidized or. othersuitable type of process.

The reaction products are withdrawn 4from zone I'G through .line l1 and,in accordance with the embodiment o1' the invention herein illustrated,are directed through line 3 into zone 4, wherein benzene and xylene areseparated and withdrawn therefrom in the manner heretofore set forth.Any unconverted toluene is likewise separated in zone 4 and may berecycled by way of lines 8 and 9 to zones I6 for further conversiontherein. .It is within the scope of the inventionto separate thereaction products from zone i8 inv a separation zone independent of zone4. However, in the preferred embodiment ofthe present invention, thevreaction products from all three conversion steps of the process mayconveniently be separated in common zones. thus providing a unitary andclosely cooperative process and avoiding the cost of additionalseparation equipment.

The trimethylbenzene separated in zone 4 and withdrawn therefrom throughline Il maybe directed through line I4. wherein it is commingled withthe benzene withdrawn from zone 4 and directed' through lines 6 and 1,and the mixture` is supplied to alkyl transfer zone. I8 which may besimilar to or dierent in designl than zone i6. In zone I8, thetrimethylbenzene is reacted'with the benzene in the presence of thecatalyst to produce xylene.` This reaction may be effected at atemperature within the range of from about 400 to about '100 C..apressure of substantially atmospheric to about 1000 pounds .on more persquare inch and with hourly weight space ve,

any, is removed from the process through line 8. The ethylbenzene maybereacted in the presence of a silica-alumina catalyst at a temperatureof from about 200 to about 600 C. and preferably within the range ofv250 to 550 C. to produce di-ethylbenzene. Temperatures of about 400 toabout 550 C. are preferred for producing ortho-di-ethylbenzene. Thereaction products in an independent system to recover medi-ethyl@benzene or the reaction productsmay be directed through lines lland 3 toseparation zone 4 wherefrom the di-ethylbenzene may be recovered throughline l5. These products' may then be subjected to further separation, bywell known means,` to recover the ortho andgotherdl-ethylbenzenes. Y

The following examples are introduced to further illustrate one specificoperation oi' the process. but not with the intention of unduly limitingthe same. Example I A straight run gasoline fraction containinghydrocarbons having 6 to 9 carbon atoms per molecule may be subjected toaromatization in the presence of an 'alumina-chroma' catalyst at atemperature of 540 C., spacevelocity of0.2 and approximately atmosphericpressure. The reaction products will contain more than 60% aromatichydrocarbons including benzene, 4toluene and trimethylbenzene.

, The toluene may be subjectedl to reaction in -the presence of asilica-alumina`- catalyst at a temperature of 600 C., atmosphericpressure and' A a space velocity of 1. Under these conditions,

a xylene fraction amounting to about 11% by weight of the toluenecharged per -pass is ob" tained, along with approximately an equalmolecular proportion of benzenel The benzene is commingled with .thetrimethylbenzene fraction and the mixture is subjected to alkyl transferin the presence .of a silica-alwmina catalyst at a temperature of about550C., atmospheric pressure and a weight hourly space velocity of l.Under these conditions there is produced a xylene fraction amounting toabout 28% by weight of the trimetlurlbenzene(charged per pass to thisstep of the process.

Example II In this example an ethylbenzene fraction was subjected toalkyl transfer in the presence of a silica-alumina catalyst at atemperature of 300 C., and a pressure of 500 pounds per square inch toproduce 20% per passof di-ethylbenzeneby weight based upon theethylbenzene'charged to this step of the process. l

We claim as our invention:

1. A process forl producing 'a d ialkyl aromatic hydrocarbon whichcomprises reacting a monoalkyl aromatic hydrocarbon in the presence of acatalyst comprising a composite of silice. and alumina at a temperatureof from about'200" to about 700 C. and an hourly weight space velocityof from about 0.1 to about 10.

2. A process for producing xylene which comprises reacting toluene inthe presence of a catalyst comprising a composite of silica and aluminaat a temperature of from about 500 to about 700 C. and an hourly weightspace lvelocity of from about 0.1 to about 10.

3. A process for producing dl-ethylbenzene which comprises reactingmono-ethylbenzene in said' monoalkyl benzene fraction in a rst reacfromzone I6 may be subjected to fractionation 1o tion zone in the presenceof an alkyl transfer amm reproduce a mami benzene' and benzene,separatingsaid benzene and reacting the same with said trialkyl benzenevfraction in a second reaction zone in the presence of an alkyl transfercatalyst to produce additional quantities of said dialkyl benzene,and'recovering the d1 alkyl benzene produced in each of said zones.

5. A process for the production of xylene which comprises separatingfrom a mixture of alkylated benzenes a toluene fraction and atrimethylbenzene fraction, reacting' said toluene fraction in a rstreaction zone in the presence ofA an alkyl transfer catalyst to producebenzene and xylene, separating said benzene and reacting the same withsaid trimethylbenzene fraction in a second reaction zone in the presenceof an alkyl transfer catalyst to produce xylene, and recovering thelxylene produced in each of said zones. y

6. A process for the production of dialkyl benzenes which comprisesintroducing a mixture of alkylated benzenes into a separation zone;introducing into said separation zone reaction products obtained ashereinafter described; removing from said separation zone a monoalkylbenzene fraction, a dia1kyl-benzene fraction,va trialkyl benzenefraction, and a benzene fraction; react; ing said monoalkyl benzenefraction in a first reaction zone in the presence of an alkyl transfercatalyst to -produce a dialkyl benzene and benzene; introducing thereaction products from said first reaction zone comprising dialkylbenzene, benzene and unconverted monoalkyl benzene into said separationzone; reacting said trialkyl benzene fraction with said benzene fractionin a second reaction zone in the presence of an alkyl `-molecule into aseparation zone; introducing into said separation zone reaction productsobtained l as hereinafter described; removing from said separation zonea benzene fraction, a toluene fraction, a xylene fraction, and atrimethyl benzenev in that the Valkyl transfer catalyst employed in eachof said reaction zones comprises a composite of silica and alumina.

9.- The process of claim 6 further characterized `in that the alkyltransfer catalyst employed in each of said reaction zones comprises acomposite A of silica and alumina,

10. A process for the production of xylene which comprises introducing amixture of alkyl.- ated benzenes containing 7, Band 9 carbon atoms permolecule into a separation zone; introducing into said separation zonereaction products obtained as hereinafter described; removing from saidseparation zone a benzene fraction, a. toluene fraction, a xylenefractionand a trimethylbenzene fraction; reacting said toluene fractionin a first reaction zone at a temperature of from about 500 C. to about700 C. and an hourly weight space velocity of from about 0.1 to about`10 in the presence of an alkyl transfer catalyst comprising a compositeof silica and alumina to produce xylene and benzene; introducingreaction products from said first reaction zone comprising benzene,xylene and unconverted toluene into said separation zone; reacting saidbenzene fraction with said trimethylbenzene fraction in a secondreaction zone at a temperature of from about.400 C. to about 760 C. andan hourly weight space velocity of from about 0.1 to about 10 in thepresence of an alkyl transfer catalyst comprising a composite of silicaand alumina to produce xyiene; introducing the reaction products fromsaid second reaction zone into said separation zone; and recovering saidxylene fraction.

11, The process of claim 10 further characterized in that cumene isrecovered from said sep- `aration zone as a product of the' process.

WAYNE L. BENEDICT. WILLIAM J. MATTOX.

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